Clamping device



Jan. 26, 1960 E. D. DILLING CLAMPING DEVICE Filed Oct. 18, 1957 Agent FIG.4.

mmvron Elmer D. Dilling v BY m CLAMPIN G DEVICE Elmer D. Dilling, Las Vegas, Nev., assi'gnor to Titanium Metals Corporation of America, New York, N.Y., a corporation of'Delaware This invention relates to a clamping device and more particularly to an electrical contact clamp adapted for clamping sheet during a stretching operation.

The manufacture of metallic sheet often involves a stretching operation to flatten or level the sheet. Stretching machines may be designed in many ways, however, they generally comprise a fixed head and a movable head which may be powerfully forced apart and cause the sheet, clamped between the two heads, to be stretched and levelled. Often sheet is heated in order to facilitate the stretching and leveling operation. A convenient method for heating metallic sheet is to pass electric current therethrough to raise the temperature of the sheet by what is termed resistance heating. It is convenient in such processes to transfer electric current to the ends of the sheet through the clamp by which the sheet ends areclamped. An electrical contact clamp therefore must perform two functions, first to clamp the end of the sheet very tightly to avoid slippage and second to provide a good electrical contact to the sheet so that heavy electrical currents employed for resistance heating may be efficiently transferred. Previously designed clamps and clamping devices have not provided the desired combination of effective clamping and efficient current transfer.

It is therefore the principal object of this invention to provide an improved clamping device. A further object of this invention is to provide a clamp which also serves as an electrical current contact device. These and other objects of this invention will be apparent from the annexed drawings in which Fig. 1 shows a general side view of a device embodying features of this invention. Fig. 2 shows a top view of the device of Fig. 1. Fig. 3 shows a section of the device of Fig. 2 taken along the lines 33. Fig. 4 illustrates, in an enlarged detailed view, the operation of the device of Fig. 1 to produce clamping and electrical contact action on the end of a sheet.

Referring now to Figs. 1, 2 and 3, the illustrated embodiment of this invention comprises a relatively massive body having a rigid upper jaw member 12 and a lower rigid jaw member 14. The upper surface of lower jaw member 14 is covered with plate 16, of electrically conductive material, advantageously of copper, fixedly attached thereto as by bolts 18 which transfix an overhanging portion 20 thereof. Detent 22 is conveniently provided in the upper surface of jaw member 14 to engage a notch in the under surface of plate 16 to maintain plate 16 on jaw 14 and immovable against strong tension forces. Plate 16 is characterized by a smooth upper surface 24. Electrical power connecting means are associated with plate 16 conveniently by provision of terminal 26 which is tightened into good electrical contact therewith by one of bolts 18.

Upper rigid jaw. member 12 is provided with pivoted dog 28. Bearing member 30 of dog 28 mates with socket 32 in upper jaw 12, the dog 28 being retained in the pivoting relationship by bearing bracket 34 which is fixedly attached to the outer under surface of upper jaw member 2,922,872 Patented Jan. 26, 1960 12 as by bolts 36. Dog 28 is further characterized by its arcuate lower surface 38 which is additionally provided with serrations or knurls 40.

Means. are provided for urging dog'28 downwardly in gripping contact with a sheet 41 disposed between dog 28 and plate 16 on the lower jaw member 14. In the embodiment illustrated, such means comprise hydraulic cylinder 42 which is mounted on jaw member 12 over bore hole 44. Piston 46 is provided in cylinder 42, and its attached piston rod 48 passes through bore hole 44 and whose lower end terminates in foot member 50, which is engageable with a corresponding depression 52 in the upper surface of dog 28. Hydraulic fluid, such as oil under pressure, admitted to the interior of cylinder 42 above piston 46 through connecting pipe line 54 will force piston 46, piston rod 48 and foot member 50'downwardly to force the dog 28 in compressive gripping engagement with sheet 41 placed on top of plate 16.

The inner end of dog 28 is provided with slot 62 in which. is disposed the lower end of connecting arm 64 which is p'i'votably attached to piston rod foot 50 as at 68. Catch pin 79 is fixedly attached to and projects laterally from the lower end of arm 64 and engages in groove 72 in a side wall of slot 62. Oil, under pressure, admitted to the interior of cylinder 42 underneath the piston 46 through pipe line 74 wil raise piston 46 and acting through piston rod 48 and its foot member 50, which is connected to arm 64, the pin 70 will, through engagement with the upper end of slot 72, raise the inner end of dog 28 toward the position shown in Fig. 3.

The clamping device of this invention employed in conjunction with sheet stretching apparatus may be conveniently fixedly fastened to a projecting element thereof, as for example, bar 76 by bolts 78.

In operation of the device of this invention the end of sheet 41 is disposed between dog 28 and plate 16 substantially as shown in Fig. 3. Oil is then introduced above piston 46 in cylinder 42 through pipe line 54 from a suitable and conventional supply source not shown. Oil pressure above piston 46 forces this member and piston rod 48 with its attached foot 50 resulting in a forceful downward movement of the inner end of dog 28. As this occurs, the serrations or knurls 40 011 the lower surface of dog 28 bite into the upper surface of sheet 41. At the same time, due to the arcuate form of the lower surface 38 of dog 28 and its natural rotation about bearing member 30 acting as a pivot the sheet 41 is moved slightly away from the inner ends of the jaw by the outward wedging action of dog 28, and when the sheet is finally clamped it will be moved to a new position as shown somewhat exaggerated for clarity, in Fig. 4. Movement of sheet 41 during the clamping operation results in a wiping motion of its under surface against the upper surface of plate 16 with which it is in contact. This wiping motion results in a clean surface to surface contact between these elements and excellent electrical current transfer characteristics. The device of this invention is simple in construction and operation. It provides excellent clamping capacity and also provides good electrical current transfer between the clamp and the end of a sheet clamped thereby.

I claim:

1. A clamping device comprising a body having rigid upper and lower jaw members, a plate of electrically conducting material and having a smooth upper surface fixedly maintained on the upper surface of said lower jaw member and having electric power connecting means associated therewith, a dog pivotably attached to the outer under surface of said upper jaw member, said dog having a convex, knurled lower surface, and means for the urging the said lower surface of said dog into gripping engagement with a sheet disposed between said dog and I said lower jaw.

conducting material and having a smooth upper surface 2,922,872 Q r j a fixedly maintained on the uppertsurface of said lower jaw member and having electric power connecting means associated, therewith, a dog pivotably attached to'the outer under surface of said upper'jaw member, said dog having a depression in the top surface thereof and a convex, knurled lower surface, a hydraulic cylinder mounted on said upper jaw over said bore hole, a piston in said cylinder having a piston rod attached thereto and passing fixedly maintained on the upper surface of said lower jaw member and having electric power connecting means associated therewith, a dog pivotably attached to the outer under surface of said upper jaw member, said dog having a convex, knurled lower surface, hydraulic cylinder and piston actuated means for urging the said lower surface of said dog into gripping engagement with a sheet disposed between said dog and said plate on said lower jaw whereby such gripping engagement of said dog urges such conducting plate on said lower jaw.

3. A clamping device comprising a body having rigid upper and lower jaw members, said upper jaw having between such sheet and the smooth upper surface of said sheet outward from said device resulting in wiping action 7 l a vertical bore hole therein, a plate of electrically conp, ducting material and having a smooth upper surface through the bore hole in said upper jaw, said piston rod lower end terminating in a foot member engageable in the depression in the upper surface of said dog for urging the said lower surface of said dog into gripping engagement ,with a sheet disposed between said dog and said plate on said lower jaw whereby such gripping engagement of said dog urges such sheet outward from said device resulting in wiping action between such sheet and the smooth upper surface of said conducting plate on said lower jaw.

References Cited in the file of this patent I p UNITED STATESPATENTS 458,177 Lemp Aug. 25, 1891 458,188 Rasmussen Aug. 25-, 1891 2,162,133

Spire June 13, 1939 

